matlab solve gives wrong output

I try to solve following equations with this code:

First i declare some parameters:

d35y=5;
d35z=5;
d37y=10;
d37z=10;
d57y=5;
d57z=5;

F3y = 10;
F3z = -20;

Then i declare the variables and solve it:

syms F5y F5z F7y F7z;

a = - F5y + F7y - F3y;     
b =  F5z + F7z + F3z;    
c =  -(d57z*F7y) + (d57y*F7z) - (d35z*F3y) - (d35y*F3z); 
d = (d35y*F5z) - (d35z*F5y) + (d37y*F7z) + (d37z*F7y);

[F5y, F5z, F7y, F7z] = solve(a,b,c,d);

F5y = double(F5y)
F5z = double(F5z)
F7y = double(F7y)
F7z = double(F7z)

As output it SHOULD give me (when i calculate it by hand it is correct):

F5y = -20
F5z = 40
F5y = -10
F5z = -20

However MATLAB gives me this as output:

F5y =   -20
F5z =   -10
F7y =    40
F7z =   -20
--> which is *not* correct.

Why does MATLAB gives me an incorrect answer?

Thanks in advance !

Answer 1

[Walter Roberson]

Try specifying the order of the variables explicitly,

[F5y, F5z, F7y, F7z] = solve(a,b,c,d, F5y, F5z, F7y, F7z);

Alternately, return an output structure

sol = solve(a,b,c,d);
[sol.F5y, sol.F5z, sol.F7y, solve.F7z]

[Nick Haverals]

Thanks a lot for your answer.

You are right, it works and gives a correct solution.

But why doesn't it work with my code, when it on another computer of a friend works (same version of matlab, exactly the same code)?

[Walter Roberson]

Is it possible that one of the two has Maple installed as the symbolic toolbox?

The order you used for the variables is what is documented, which is to say the order used by symvar() which should have sorted the way you wanted. But I never count on that ordering, which is a bit odd.